This invention relates to an apparatus and a method for injection molding molten material such as plastic, and more particularly, to an apparatus and a method for producing injection molding product separated from a runner in molds, and for injection molding thinly in molds. 2. Description of Related Art
In the conventional technique for injection molding, as disclosed in Japanese Patent Laying Open Publication No. Heisei 2-220824, a cutter projects ahead at the same time as a cutter bed retreats, when a movable mold is separated from a stationary mold, so that a cutting edge cuts a gate, then product is separated from a runner automatically.
In another conventional technique for injection molding, as disclosed in Japanese Patent Laying Open Publication No. Heisei 4-288010, a gate cut pin projects ahead and cuts a gate, when molten plastic maintain some plasticity and a skin layer is formed. Then, products are cut from a runner after molten plastic hardens by cooling.
In another conventional technique, a press forming pin projects in a cavity, so that thin plastic is formed between this pin and an against mold surface.
However, in the 2-220824 technique, strong force is needed. It is difficult to cut hardened plastic without strong force, as a gate is cut after forming. Sometimes, broken pieces of plastic scatter when the product is cut by force. It takes much time to remove the pieces.
In the 4-238010 technique, strong force is needed to separate product, as molten plastic is pressed out by a gate cut pin to rise the pressure in the molds, when the gate cut pin projects ahead into molten plastic in case of cutting a gate.
In the thin molding technique, it needs strong force to mold thinly, as molten plastic is pressed out by a pin to rise the pressure in the molds, when a press molding pin projects same as the 4-238010.